(1) Field of the Invention
The present invention relates to the storage and generation of arbitrary waveforms. More particularly, the invention relates to a system for storing a digital representation of an analog waveform and for generating a desired analog waveform from the stored digital data.
(2) Description of the Prior Art
There are many applications which require the production of arbitrary waveforms. For example, arbitrary waveforms are often used to calibrate and/or to test the response of various devices to specific signals (waveforms). In such applications, an arbitrary waveform generator produces a desired output waveform and the response to the waveform is measured and analyzed, enabling one to modify or correct the device.
Often such testing and calibration must be performed in remote locations. In such locations, it is desirable to have a small, portable, rugged device available to synthesize and generate complex arbitrary waveforms. For example, the U.S. Navy uses arbitrary waveform generators to produce sonar waveforms which are used to calibrate and test acoustic sensors, unmanned underwater vehicles, and counter measure devices. These applications, which are often performed at sea, require the production of complex arbitrary waveforms at various locations and depths. Additionally, because nearby objects such as the hull of a ship can cause echoes which interfere with the waveform, the waveform generator should be operated at a distance from nearby objects, thus directing a need for small, portable devices which require little power to operate. Furthermore, because it is often necessary to synthesize waveforms during the testing, the waveform generator should be relatively easy to program.
Arbitrary waveform generators presently in use fall into two general categories, frequency synthesizers and read only memory (ROM) devices. While frequency synthesizers and ROM devices are capable of providing the analog waveforms necessary for calibrating or testing various devices, they generally suffer from one or more disadvantages which limit their use for many applications. Frequency synthesizers are generally costly, bulky and fragile instruments limited to laboratory use. Frequency synthesizers also tend to be tedious and time consuming to program for the generation of arbitrary waveforms. Thus, frequency synthesizers are unattractive for applications requiring a rugged, portable waveform generator to produce complex, arbitrary waveforms which cannot be well defined using mathematical formulas.
ROM devices generally require sophisticated hardware and software for programming and are often used under microprocessor control for playback. Microprocessor programmed control of the output waveform generally requires the addition of timer loops and adds interrupt service overhead, thus reducing the availability of the microprocessor to perform other tasks. The microprocessor and ROM programmer also substantially add to the weight, cost and power consumption of ROM based waveform generators. The size, cost, complexity and power consumption of ROM based waveform generators, as well as cost and time associated with programming ROM devices make the use of ROM based waveform generators prohibitive for generating complex, arbitrary waveforms in remote locations.
There is currently no small, portable, rugged device available to synthesize and generate arbitrary waveforms. The high cost of current waveform generators, their size, complexity, power consumption, lack of ruggedness as well as the difficulty in generating complex, arbitrary waveforms restrict the use of existing waveform generators for applications performed in remote locations.